The PON (Passive Optical Network, PON) technology is a point to multi-point (P2MP) optical access technology. A PON includes an optical line terminal (Optical line terminal, OLT), an optical splitter (Optical splitter) or extender box (Extender Box, EB), optical network units (Optical Network Unit, ONUs) or optical network terminals (Optical Network Terminal, ONTs), and optical fibers connecting these devices. The OLT, as a device at the central office end, is connected to the optical splitter or EB through a feeder fiber, and the optical splitter or EB is connected to each ONU through a separate drop fiber. A feeder fiber exists between the optical splitter or EB and the OLT, and several drop fibers exist between the optical splitter or EB and the ONUs. In the downlink direction (OLT->ONU), the optical splitter or EB implements optical splitting function and sends the downlink optical signals of the OLT to all ONUs through drop fibers. In the uplink direction (ONU->OLT), the optical splitter or EB converges optical signals sent by all ONUs and sends the signals to the OLT through the feeder fiber.
At present, to handle failures of the feeder fiber between the optical splitter or EB and the OLT or failures of the OLT, the 1+1 protection architecture shown in FIG. 1 is usually applied. The architecture uses two sets of working/protection feeder fibers and OLTs to provide 1+1 protection for the feeder fiber and OLT. When the working feeder fiber or OLT fails, the protection OLT takes over the ONU under the previously working OLT.
Though the solution may protect the feeder fiber and OLT, each OLT needs a protection OLT and the network construction cost is high. As a result, access applications of enterprise users and dedicated line users of the PON are hindered.